Best base layers for women UK 2023: stay cosy and comfortable with thermal base layers for outdoor adventures

Base layers are what Icebreaker do best, and they’re always some of the top-performing designs when we test out base layers.

£75 (top), £60 (bottoms)

If you want to invest in a great set of thermal underwear, our pick of the pack are their Oasis base layer top and their Everyday Thermal leggings.

Slip them on and the first thing you’ll notice is how deliciously soft their 100% Merino wool make-up feels against the skin.

The Oasis’ 200g weight is a good warmth to weight ratio for most outdoor adventures, and the Thermal leggings live up to their name, keeping you delightfully warm even on winter hikes and ski adventures.

Icebreaker’s merino layers are worth the spend, and will last you for years without losing their shape or their warming abilities.

The bottoms are available here.

Base layers are a handy bit of kit to own – but they don’t usually get you many style points. Not so with Arc’teryx’s good-looking Motus.

What we love about this base layer is how little it looks like a base layer – this smart crewneck top looks just as good tucked into jeans as it does with walking trousers.

There’s substance as well as style here, of course – the thermal material is soft against the skin, instantly warming and also great at staying breathable when you pick up the pace.

A boxy cut means this is not the slimmest-fitting or the warmest base layer we tested, but it’s ideal for layering up for autumn adventures.

It’s probably not surprising that our top base layer for runners comes from a running brand, - Runderwear really know how to design pieces that are perfect for keeping keen road and trail runners warm.

This long-sleeved top is stretchy and slim-fitting without being restrictive – it moves so well when you’re jogging that you’ll barely notice you have it on as you clock up the miles.

This is also one of the most breathable base tops in our round-up, great for keeping you warm without overheating on cold weather runs, and even sports built-in mitts you can pop on if your hands get chilly. A short-sleeved version is also launching this autumn.

Get cosy when the mercury drops in a cold weather-specific base layer.

Ideal for skiing, hiking or winter camping (where they also double up as great sleepwear), Jack Wolfskin’s Iseler Tights W are super warm and comfy, wick away sweat well if you do raise your body temperature and are suitable for wearing in their namesake Arctic conditions.

The only thing to note is that these tights are slightly see-through, so while they make a great base layer for winter sports, they don’t really work as standalone leggings that you could wear to après ski.

A great base layer top for under £30? You can with Alpkit’s Koulin, a simple, flattering and reliably warm long sleeve top that’s ideal for hiking trips.

We love the bright berry colour and the slim, feminine fit, which is flattering without being too figure-hugging.

The Koulin is breathable if you sweat and also uses Polygiene technology to keep odours at bay – ideal if you’re on a multi-day walk or are camping far away from civilization. There’s even a back pocket for stashing snacks. A bargain!

£49 (top) £59 (bottoms)

Pleasingly soft and comfortable to wear and with some of the best stretch of all the base layers we tested out, Acai’s warm top and bottoms have clearly been designed with womens’ bodies in mind - they move as you do and hold their shape well after a wash, too.

We like the wide crew neck and longer cut of the top, and the thick, comfy and flattering high waistband of the trousers, which work brilliantly for everything from running to yoga, and are smart enough to wear casually when you aren’t getting active.

We’ve never come across a base layer top designed to improve your posture before, but that’s exactly what CEP reckon their technology does – sensory stripes of material down your shoulder blades help you tell if you’re holding your back and neck correctly.

You may have to wear this figure-hugging top a few times to get used to it, but anything that helps with better running or hiking, especially if you usually wear a heavy backpack, is a great idea in our book.

We also like the longer cut and stretchy material, which keep the top comfortably in place as you move – great for joggers.

Haglofs was founded in Sweden, so it’s not a surprise that they have an eye for cold weather gear.

Their no-nonsense 96% merino Actives range of base layers is designed with snow sports in mind, and the top and long johns are form-fitting and easy to layer, with well-placed flatlock seams that mean you’ll barely feel your thermals even as you ski or snowboard.

The top works as a wardrobe staple, but the leggings do look too much like underwear to stick on for casual use or a yoga class.

The Actives top and bottoms are pricy, but we reckon they’re worth it for serious sports lovers, considering they pack a merino wool punch that makes them ideal for long days on and off the pistes.

Layering is the key to trapping in warmth when you’re hiking in cold conditions – and Paramo’s Grid top is a brilliant top to add to the mix.

This was one of our favourite base layers on test for all day wear, and it can be worn next to the skin or as a mid layer on top of a thinner thermal top too due to its slightly looser cut.

We like the sweat-wicking grid material, the comfy wider cut, and Grid Technic’s flattering, rather retro looks. Thumb holes are also handy when you’re wearing gloves for winter sports.